Vacuum assisted resin transfer moulding (VARTM) of large structures has to date involved in the inclusion of conduits for resin distribution into the moulded structure. Examples therefore are disclosed in EP 1 310 351 B1, WO 2006/058540 A1, WO 2006/058541 A1, and WO 2007/038930 A1.
EP 1 310 351 B1 describes a mould for wind turbine rotor blades which comprises a lower mould part, an upper mould part, and a core. For forming a laminated rotor blade, fibre reinforcement layers are layered in the lower mould part and the core is put atop on the layers. Layer sections projecting over the lower mould are then wound around the core so as to overlap in the middle of the core and then the upper mould part is set atop on these layers. When the leading edge of the layer stack is formed a flow pipe is integrated into the stack of fibre reinforcement layers so as to allow for distributing resin to the layers. This flow pipe will be part of the laminated wind turbine rotor blade after curing the resin.
WO 2006/058540 A1 describes a vacuum infusion method by means of a semi-permeable membrane. In this method, a mould is applied with a mould cavity, in which a fibre insertion is placed which comprises a plurality of fibre layers and a distribution layer. The distribution layer allows for a higher rate of flow for a liquid polymer than the fibre layers. Inlet channels are located atop of the fibre insertion. The liquid polymer is directed via the inlet channels to the distribution layer after the mould has been closed by use of a vacuum bag.
WO 2006/058541 A1 describes a method and an apparatus for producing fibre composite mouldings by means of vacuum infusion. In the method, a mould with a mould cavity, a plurality of inlet channels communicating with the mould cavity, and a polymer source with liquid polymer is applied. A plurality of vacuum channels communicates with the mould cavity and a vacuum source. Fibre material is inserted into the mould cavity prior to the process of filling said mould, and where a reduced pressure is generated in the vacuum channels and thus in the mould cavity with the result that liquid polymer is drawn from the polymer source via the inlet channels into the mould cavity. One or more of the inlet channels can also communicate with the vacuum source and/or one or more of the vacuum channels can also communicate with a polymer source.
WO 2007/038930 A1 describes a method for producing a fibre reinforced product. In the method, one or more layers of reinforcing fibres are placed into the cavity of a mould. The layers are covered with a resin distribution member over which a number of resin inlets which are formed by pipes are placed. The resin distribution member can be removed after producing the laminate. Alternatively, the resin distribution member and the inlets can remain part of the laminate. If the resin distribution system, i.e. the inlet pipes and/or the resin distribution layer, remains in the laminated structure, it adds to weight without providing a substantial structural benefit. On the other hand, if the resin distribution layer is removed from the laminated structure, this is an elaborate process since the distribution layer is provided on a large fraction of the finished structure's surface area.